Turkish Journal of Biology




Phaseolus seedlings (Phaseolus vulgaris L.) in light conditions were treated with 2 different concentrations of 2 heavy metals, mercury (0.05 mM and 0.4 mM) and chromium (0.5 and 1.0 mM). Mercury was given in the form of HgCl_2 and chromium was given in the form of K_2Cr_2O_7. Peroxidase activity was measured with 4 different hydrogen donors (ferulic acid, caffeic acid, pyrocatechol and pyrogallol). Both mercury and chromium inhibited root and hypocotyl length. The inhibition was about 50%-80%, depending on the concentration of the heavy metal. Peroxidase and IAA oxidase activities showed a clear inverse relation with growth. Seedlings treated with a lower concentration of mercury had similar activities to those treated with higher concentrations of chromium. The role of peroxidase and IAA oxidase activities in defense mechanisms in response to heavy metal toxicity is discussed.


chromium, mercury, metal toxicity, peroxidase activity, defense mechanism

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